page_title: Ordnance Survey
section_title: 20th century
hierarchical_section_title: Ordnance Survey / 20th century
caption_attribution_description: English: A stitch of scans of Ordnance Survey 1:63360 seventh series sheet 170 London S.W. published 1959. 1962 reprint.
context_page_description: Ordnance Survey is the national mapping agency for Great Britain. The agency's name indicates its original military purpose, which was to map Scotland in the wake of the Jacobite rising of 1745. There was also a more general and nationwide need in light of the potential threat of invasion during the Napoleonic Wars. Since 1 April 2015 Ordnance Survey has operated as Ordnance Survey Ltd, a government-owned company, 100% in public ownership. The Ordnance Survey Board remains accountable to the Secretary of State for Business, Energy and Industrial Strategy. It was also a member of the Public Data Group.
  Paper maps for walkers represent only 5% of OS' annual revenue. They produce digital map data, online route planning and sharing services and mobile apps, plus many other location-based products for business, government and consumers. Ordnance Survey mapping is usually classified as either "large-scale" or "small-scale". The Survey's large-scale mapping comprises 1:2,500 maps for urban areas and 1:10,000 more generally. These large scale maps are typically used in professional land-use contexts and were available as sheets until the 1980s, when they were digitised.
context_section_description: During World War I, the Ordnance Survey was involved in preparing maps of France and Belgium. During World War II, many more maps were created, including:
  1:40,000 map of Antwerp, Belgium
  1:100,000 map of Brussels, Belgium
  1:5,000,000 map of South Africa
  1:250,000 map of Italy
  1:50,000 map of north-east France
  1:30,000 map of the Netherlands with manuscript outline of districts occupied by the German Army.
  After the war, Colonel Charles Close, then Director General, developed a strategy using covers designed by Ellis Martin to increase sales in the leisure market. In 1920 O. G. S. Crawford was appointed Archaeology Officer and played a prominent role in developing the use of aerial photography to deepen understanding of archaeology.
  In 1922, devolution to Northern Ireland led to the creation of Ordnance Survey of Northern Ireland (OSNI) and independence of the Irish Free State led to the creation of the Ordnance Survey of Ireland, so the original Ordnance Survey pulled its coverage back to Great Britain.
  In 1935, the Davidson Committee was established to review the Ordnance Survey's future. The new Director General, Major-General Malcolm MacLeod, started the retriangulation of Great Britain, an immense task involving the erection of concrete triangulation pillars ("trig points") on prominent hilltops as infallible positions for theodolites. Each measurement made by theodolite during the retriangulation was repeated no fewer than 32 times.
  The Davidson Committee's final report set the Ordnance Survey on course for the 20th century. The metric national grid reference system was launched and a 1:25000-scale series of maps was introduced. The one-inch maps continued to be produced until the 1970s, when they were superseded by the 1:50000-scale series – as proposed by William Roy more than two centuries earlier.
  Ordnance Survey had outgrown its site in the centre of Southampton (made worse by the bomb damage of the Second World War). The bombing during the Blitz devastated Southampton in November 1940 and destroyed most of Ordnance Survey's city centre offices. Staff were dispersed to other buildings and to temporary accommodation at Chessington and Esher, Surrey, where they produced 1:25000 scale maps of France, Italy, Germany and most of the rest of Europe in preparation for its invasion. Until 1969, Ordnance Survey largely remained at its Southampton city centre HQ and at temporary buildings in the suburb of Maybush nearby, when a new purpose-built headquarters was opened in Maybush adjacent to the wartime temporary buildings there. Some of the remaining buildings of the original Southampton city-centre site are now used as part of the city's court complex.
  The new head office building was designed by the Ministry of Public Buildings and Works for 4000 staff, including many new recruits who were taken on in the late 1960s and early 1970s as draughtsmen and surveyors. The buildings originally contained factory-floor space for photographic processes such as heliozincography and map printing, as well as large buildings for storing flat maps. Above the industrial areas were extensive office areas. The complex was notable for its concrete mural by sculptor Keith McCarter and the concrete elliptical paraboloid shell roof over the staff restaurant building.
  In 1995, Ordnance Survey digitised the last of about 230,000 maps, making the United Kingdom the first country in the world to complete a programme of large-scale electronic mapping. By the late 1990s technological developments had eliminated the need for vast areas for storing maps and for making printing plates by hand. Although there was a small computer section at Ordnance Survey in the 1960s, the digitising programme had replaced the need for printing large-scale maps, while computer-to-plate technology (in the form of a single machine) had also rendered the photographic platemaking areas obsolete. Part of the latter was converted into a new conference centre in 2000, which was used for internal events and also made available for external organisations to hire.
  The Ordnan
caption: Detailed scan of a complete 7th series sheet
exif: {"Image XResolution": "600", "Image YResolution": "600", "Image ResolutionUnit": "Pixels/Inch", "Image Software": "Microsoft ICE v1.4.4.0", "Image DateTime": "2014:04:30 09:55:21", "Image Tag 0x4748": "[1, 0, 0, 0, 4, 0, 0, 0, 0, 0, 0, 0, 165, 97, 15, 190, 35, 184, 229, 61, 249, 149, 27, 190, 74, 115, 28, 62]", "Image ExifOffset": "186", "EXIF DateTimeDigitized": "2014:04:30 09:55:21", "EXIF ColorSpace": "sRGB"}